Maximum intensity for monochromatic (single-color) light from two sources occurs where the difference in distances from the sources is an integer number of wavelengths. Find the equation of the curves of maximum intensity in a thin film between the sources where the difference in paths is two wavelengths and the sources are four wavelengths apart. Let the sources be on the x-axis and the origin midway between them. Use units of one wavelength for both x and y.